The photo if I read the caption correctly is of part of the 5th Australian Commonwealth Horse Regiment raised in March-April 1902 under the command of Lt Col James Macarthur Onslow. Macarthur Onslow had completed a tour of duty in the war as a staff officer on General Porter and General Hutton's HQ . Regarded as too old for field service in WW1 he saw service with the Sea Transport Service of the Australian Imperial Force and retired as a Major General. This regiment was sometimes described as the finest to leave NSW but arrived after peace was signed and thus saw no service. This was a NSW Regiment -one of 8 raised by Australia in 1902 to replace all Australian State Regiments except the 3rd NSW Imperial Bushmen (It thus becoming the 9th Australian unit in the line in South Africa) which remained on duty in theatre under the command of Lt Col the Hon Rupert Carington CVO DSO later Lord Carrington and grandfather of the current holder of the title. Carington a former Grenadier guardsman actually spent more time in Australian uniform than British uniform retiring in 1916 as a Colonel commanding a Light Horse Brigade on home service in Australia

The other point to make is that the photo caption is in error when it talks about the Commonwealth Light Horse, The correct title was Australian Commonwealth Horse abbreviated to ACH. The Concept of "Light Horse" did not exist in the Australian Army until after 1903 when the then Commandant of the Army, Sir Edward Hutton mandated that Australian mounted units would be based on the Light Horse principle. By this he meant that they would be based on the concept of US Cavalry but without swords. The term Light Horse was used rather than Mounted Rifles to stress that these units were not just mounted infantry but had a cavalry function including long range recon and deep penetration. Some units such as the NSW Lancers managed to hang onto their cavalry accoutrements but all units were titled Light Horse with their regional or historical title in brackets